<!DOCTYPE html>
<html>
<head>
<style type="text/css">
fieldset {
 height: 20px;
 padding: 0;
 border: none;
 background-color: green;
}
#top {
 margin: 0 0 10px;
}
#middle {
 margin: 20px 0;
}
#bottom {
 margin: 10px 0 0;
}
</style>
</head>
<body>
<fieldset id="top"></fieldset>
<fieldset id="middle"></fieldset>
<fieldset id="bottom"></fieldset>
</body>
</html>
